Extranuclear recombination in Aspergillus nidulans: closely-linked multiple chloramphenicol- and oligomycin-resistance loci.

A nuclear, chloramphenicol-sensitive mutant cas-1 has been isolated which is cross sensitive to a number of drugs, including oligomycin and cycloheximide. Approximately one-third of the chloramphenicol-resistant mutants isolated from mutagenized conidia of this strain were found to be extranuclear, and exhibited a variety of phenotypes. One of these mutants, designated (camB51), was slow growing on drug-free medium and recombined at low frequency with the previously described mutant (camA112) (Gunatilleke et al., 1975). The majority of extranuclear oligomycin-resistant mutants isolated from cas-1 were indistinguishable from (oliA1) (Rowlands and Turner, 1973). Two mutants, (oliB322) and (oliB332), with similar but not identical phenotypes to (oli A1), recombined with the latter at low frequency but not with each other, thus representing a new class of extranuclear mutants.